1. Field of the Invention
The present invention relates to improvements in multispectral imaging for determining the characteristics of an objects, and more particularly to improvements which are capable of providing imaging of internal structure through trans-illumination apparatus and techniques.
2. Description of Related Art
The human visual system is able to detect light in a range of wavelengths that are typically described as “visible light.” The longest wavelengths detected are red, the mid range is green and shortest wavelengths are blue. Long wavelength light such as infrared and short wavelength light such as ultraviolet are invisible to the human eye. The characteristics of an object that we can determine with the unaided eye are limited to those that can be detected in this spectrum. Furthermore, the trichromatic system used by the eye is broadband in nature and cannot see narrowband artifacts such as would be seen by a spectrophotometer.
Several products have reached market that emit infrared light on an object and use the reflected light to detect a pattern of varying contrast in the infrared spectrum. The device then projects an image that follows those contrast changes using a wavelength within the visible spectrum. In one such product, the AccuVein AV300, detects a pattern of absorption and reflection in the infrared and re-projects that pattern as red. Given that hemoglobin absorbs infrared light to a greater degree than the surrounding tissue, the projected pattern can be used by a medical practitioner to identify the position of a vein to be used for venipuncture.
In other products, the light is captured and the processed image is displayed on a remote screen such as an LCD panel or through an eyepiece that is in line with the object.
These contrast enhancement products act as color shifters. Just as the human eye would detect variations in absorption and reflection in the three colors it can see (red, green and blue), these contrast enhancers detect the variations at wavelengths outside the visible spectrum and display the corresponding pattern inside the visible spectrum.